Nucleic acids (DNA=deoxyribonucleic acid, RNA=ribonucleic acid) are frequently used as a starting material for various analyses and assays in medical and pharmaceutical research, clinical diagnosis and genetic fingerprinting which typically require high quantity nucleic acids input.
As a matter of routine, adequate quantities of nucleic acids may be readily obtained by means of in-vitro amplification techniques, e.g., based on the well-known polymerase chain reaction (PCR). Commonly, prior to amplification, extraction (purification) of nucleic acids is required which can be performed in a two-step process, with a first step of releasing the nucleic acids from their envelopes (e.g. cell membranes) and a second step of separating the released nucleic acids from the remainder.
While nucleic acids may be readily released by incubating the samples, separation of the released nucleic acids is somewhat more difficult. The nucleic acids, for instance, may be separated making use of the differing molecular weights of the various cell components in a centrifuge. Spinning down the cell components typically results in different density layers, so that the nucleic acids may be selectively removed by a pipette or any other suitable instrument. Another separation technique that has been in practical use since several years and, for instance, is described in U.S. Pat. No. 5,973,138, uses magnetically responsive particles, which can be made to bind reversibly to the nucleic acids. Applying a magnetic field causes the particle-bound nucleic acids to be drawn to and be held against the inner wall of the vessel containing the cell components, enabling the surrounding medium to be flushed away and replaced by another fluid to re-suspend the nucleic acids therein.
In consideration of the fact that there is an ongoing increase in genetic analyses and assays requiring amplified nucleic acids, a strong demand for the automated extraction of nucleic acids prior to their amplification is observed.
International patent application WO 00/45164 describes a robotic workstation for the automated extraction and amplification of nucleic acids. In such workstation, multi-well plates to be filled with the samples are arranged on a rotary deck that can be revolved around a central column. A tool mount block that may simultaneously be provided with several tools can be moved vertically along the central column, so that alignment of the multi-well plates with each of the tools can be achieved revolving the rotary deck around the central column. Hence, the multi-well plates must be horizontally transferred to reach alignment with the tools, which, however, causes an undesired risk of contamination and/or spilling of the fluids. In addition, fixation of the tools at the tool mount block and rotationally transferring the multi-well plates for their alignment with the tools requires much constructional space which undesirably enlarges the overall dimensions of the work station.